Toxic Smite

The next time you hit a creature with a melee attack before this spell ends, the weapon gleams with a poisonous aura as you strike. The attack deals an extra 2d6 poison damage to the target, which then becomes must make a Constitution saving throw or become poisoned for 1 minute. The creature can repeat the saving throw at the end of subsequent turns to end the effect.  

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the extra damage increases by 1d6 for each slot level above 2nd.